Switch lock for power driven tools



Dec. 11, 1951 R. B. PEALER SWITCH LOCKFOR POWER DRIVEN TOOLS 2 SHEETS-SHEET l Filed July 30, 1948 lDecn l, 1951 R. B. PEALER 2,578,317

SWITCH LOCK FOR POWER DRIVEN TOOLS Filed July 30, 1948 2 SHEETS-SHEET 2 Patented Dec. 11, 1951 SWITCH LOCK FOR POWER DRIVEN TOOLS Robert B. Pealer, Garrettsville, Ohio, assigner to Beaver Pipe Tools, Inc., Warren, Ohio, a corporation of Ohio Application July 30, 1948, Serial No. 41,651

(Cl. 20G- 169) 9 Claims.

This invention relates to a safety lock for the controlling switch of an electrically driven power` tool. Many power driven machine tools, as for example pipe working machines, have rotary chucks the jaws of which must be set in clamping position by a removable manual wrench. Such wrench when in use usually projects radially from the chuck head. It sometimes happens that the operator forgets to remove the chuck wrench after eecting the clamping and starts the machine with the wrench still in the chuck head. The result is that the projecting wrench is carried around by the rotary chuck head and may come into engagement with the bed of the machine or some other fixed part and cause breakage of some part of the machine-usually in the transmission gears.

The object of this invention is to provide means to prevent the starting of the machine in case the operator inadverently leaves the chuck i" wrench standing in the chuck. To this end, I have provided a holding device which normally locks the switch in neutral position and has provision for supporting the chuck wrench. When the chuck wrench is put on such support it acts to release the lock from the switch lever, allowing the operator to move the switch in the usual manner.

My invention provides not only a convenient support for the chuck wrench but means auto- .g-

matically operated by such support for controlling the switch. Accordingly, if the operator inadvertently leaves the chuck wrench in the chuck and attempts to start the switch he will iind it locked by reason of the absence of the i chuck wrench on the support and will thus be prevented from starting the driving motor, and will be at once advised of the improper location of the chuck wrench.

A preferred form of my switch-locking and wrench-supporting mechanism is illustrated in the drawings hereof and hereinafter fully described and the essential novel features are set out in the claims.

In the drawings, Fig. l is a Side elevation of a machine having a motor operated hollow chuck, such as utilized in a power drive for a pipe to be threaded or in a pipe working machine; Fig. 2 is an end View of the machine shown in Fig. 1; Fig. 3

is a plan on a larger scale of my switch lever control and wrench supporting device; Fig. 4 is a vertical section through the parts shown in Fig. 3; Fig. 5 is a detail in vertical cross-section in a .plane indicated by the line 5-5 in Fig. 3.

In Figs. .1 and 2, I indicates any suitable bed and ll a hollow standard rising therefrom. In this standard is mounted a rotatable barrel i3 carrying a chuck i4. I have indicated a spur gear I on the barrel which is shown as being driven by a meshing pinion i3 from a suitable motor Il through reduction gearing contained in the casing i8. The chuck has suitable readily movable jaws IS controlled by one or more radial wrench sockets 19a, one of which is shown in Fig. 1.

In Figs. 1, 2 and 4, 2i] indicates a switch box containing suitable switch mechanism for controlling the motor. As shown the switch box is mounted directly on the motor frame. The switch mechanism has the usual operating lever 22, which projects upwardly through the cover of the box.

My wrench support and switch control is mounted directly on the switch box 2D and it takes the place of the normal cover plate for such box without in any manner changing the mechanism in the interior of the box or the upwardly projecting operating lever.

As shown, more particularly in Figs. 3 and 4, I have provided a hollow downwardly facing boxlike member to be mounted on the switch box in place of the normal covering. This box-like member comprises a top plate 39, front and back flanges 3l and 32 and two end flanges, one of which is shown at 33 in Figs. 2 and 4. These four anges make a downwardly extending rim around the top plate which is formed to occupy the external rabbet on the walls or" the box in place of the usual flanged cover plate.

On the front wall 3| with my switch box cover I provide a pair of forwardly projecting ears 35 between which is a biiurcated outwardly extending block pivoted to the ears by a pin 4|. The projecting jaws 42 of this block provide a support for the chuck wrench. A suitable torsion spring 45 surrounds the pin 4I and bears at one end against the front wall of the cover and at the other end against the underside of the bifurcated block, thus tending to raise the block.

0n top of the cover plate is a slidable locking plate which has a bifurcated rear end adapted to straddle the switch lever 22. The bifurcated block is suitably connected to this sliding plate to operate it. I have shown a lug 4l extending upwardly from the block through a hole 5| in a plate. The sliding plate is preferably guided between bosses 35 (Fig. 5) formed on the cover plate 3i) and lies beneath a small plate 37 secured to the bosses by screws 38.

It results from the described construction that the spring, if allowed to act, raises the jaws 42 c and moves the locking piate rearwardly to straddle the switch lever and hold it in idle position. When however a chuck wrench is placed on the jaws its weight swings the jaws downwardly and the lug il swinging forwardly withdraws the iocking plate 5d and thus frees the switch lever, as indicated by broken lines in Fig. 4.

The chuck Wrenches usually employed vhave a central shank indicated at A and a transverse operating lever o. The space between the jaws 42 is suiiicient to receive the shank of the wrench while the handle rests on top of the jaws. The jaws are preferably curved upwardly near their outer end as shown to retain the wrench in place when put in position.

My jaw-block carried by the switch box furnishes means in a very convenient position for supporting the wrench, where it hangs down in an idle space alongside the motor and visible from the Afront of the machine where the operator works.

.condition of the switch prevents such action and he is immediately advised that the wrench is not in its proper place for the starting of the motor. I prefer to make the box-like carrier portion of my device of such dimensions that it will readily t standard switch boxes on the market. In such case, I make at least one of the vertical flanges with a notch of considerable size, as indicated in Fig. 4, to clear the lead-in cable to the motor, in-

dicated at 25, Figs. 1, 2 and 3. To simplify the locking of my switch box cover in position I provide the top plate Si! with holes 3Q through which screws may be passed into the same threads within the switch box which normally receive the screws when holding the usual switch box cover. It will be seen that my invention accomplishes the double result of providing a very convenient readily visible support for the idle wrench and `also a safety device preventing damage to the vmachine resulting from the wrench being inadvertently left in the chuck. My device is of simple construction, inexpensive and readily applied.

I claim:

an electric motor of a machine tool, said switch having a projecting manual actuating lever, a cover for said switch havin-g an opening through Iwhich the lever projects, a locking member slidably mounted on the cover, a spring normally 'holding the locking member in an active position where it prevents effective movement of the switch lever, a support for a hand tool, and means whereby the hand tool when o-n said support is eective to move the locking member from its active' position to its inactive position Where it clears the switch lever.

2. A cover for the switch box of a machine tool,

ysaid cover having an opening through which the i switch lever may extend, a locking plate having a bifurcated rear end adapted to receive the switch lever when said lever is in neutral position, means on the cover to slidablyv guide said locking plate,

a pair of ears carried bysaid cover -at the front of 1 vtending to elevate said bifurcated support to hold the locking plate in position with its rear end embracing the switch lever.

3. The combination of a switch for controlling an electric circuit, said switch being mounted in a box and having a projecting manual actuating lever, a locking member slidably mounted on the switch box and adapted to stand in an active position where it prevents effective movement of the switch lever or in an inactive position Where it clears the switch lever, a pivotally mounted support for a weight, an operating connection between said support and said locking member and means tending to raise the support and thereby cause the locking member to assume an active position, Awhereby when the weight is placed on the support it may lower the support and automatically withdraw the locking member from its active position.

4. The combination of a switch for controlling an electric circuit, said switch being mounted in a box and having a projecting manual actuating lever, the cover for said switch box having an opening through which the manual lever projects, a locking plate slidably mounted on the cover and having a notch through which the lever in neutral position may extend, a pivotally mounted support for a weight, a spring tending to raise the support, and a connection between the support and the locking plate, whereby the locking plate is normally in locking position but may be withdrawn by a weight resting on the support.

5. The combination of a switch for controlling an electric circuit, said switch being mounted in a box and having a projecting manual actuating lever, a cover for said switch box having an opening through which the manual lever projects, said cover having a skirt adapted to extend onto Ythe front of the switch box, a pair of spaced ears carried by said skirt, a bifurcated weight-support pivotally mounted between said ears, a spring tending to swing the bifurcated support upwardly, a plate slidably guided on said cover having a notch at its rear end adapted to receive the switch lever when said lever is in neutral position, and an operating connection between the locking plate and the biiurcated support.

6. The combination of a switch ior controlling an electric circuit, said switch being mounted ,w in a box and having a projecting manual actuat 1. The combinatmn of a switch for controlling ing lever, a cover for said box having an opening through which the switch lever extends, a locking plate having a bifurcated rear end adapted to receive the switch lever when said lever is in i neutral position, means on the cover to slidably guide said locking plate, a pair of ears carried by said cover at the front of the switch box, a bifurcated weight-support pivotally mounted between said ears, said weight-support having an upwardly extending projection occupying a recess in said locking plate, and a spring tending to elevate said biiurcated support.

7 The combination of. an electric switch, said switch being mounted in a box, a bifurcated support for a hand tool, said support being pivotally mounted between ears carried on the front of the switch box, a locking plate slidably mounted on the cover of the switch box and having a bifurcated rear end adapted to straddle the switch lever when said lever is in neutral position, an operating connection between the bifurcated support and the locking plate whereby downward movement of the bifurcated support may move the locking plate forward to idle position; and-a spring acting 'on the biiurcated support and tending to raise it to maintain the locking plate in its active position.

8. The combination of a cover for a switch box having an opening through which a manual actuating lever may project, said cover having a skirt adapted to extend onto the front of the switch box, a pair of spaced ears carried by said skirt, a bifurcated tool support pivotally mounted between said ears, a spring tending to swing the bifurcated support upwardly, a plate slidabl;7 guided on said cover having a notch at its rear end adapted to receive the switch lever in neutral position, and an operating connection between the locking plate and the bifurcated support, whereby in the absence of a weight on the support the plate due to the bias of the spring will maintain the switch lever locked in neutral position.

9. The combination ci' a switch for controlling an electric circuit, said se itch having a projecting actuating lever, a plate slidably guided to move in its own plane and adapted to coact with the lever to lock the lever in its idle position or free it according to the position of the plate, a spring tending to move said plate to locking position,

6 and a lever pvotally mounted on a horizontal axis and connected to the plate and having a part which extends away from the pivot of the lever and is formed to support a weight of suiicient mass to move the lever and plate against the action of said spring.

ROBERT B. PEALER.

The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 728,590 Linn May 19, 1903 1,383,781 Ball July 5, 1921 1,659,284 Smith Feb. 14, 1928 1,829,263 Carlsen Oct. 27, 1931 1,910,217 Hadeld May 23, 1933 2,224,691 Pealer Dec. 10, 1940 2,246,919 rantz June 24, 1941 2,263,277 Schumann Nov. 18, 1941 2,444,188 Englund June 29, 1948 2,466,355 Baker Apr. 5, 1949 

